1. Field of the Invention
The present invention relates to the field of computer processing systems. More particularly, the present invention relates to the field of upgrading computer systems, particularly those employing microprocessors.
2. Art Background
Microprocessor based computer systems frequently employ printed circuit boards (PCBs) containing connectors or sockets which physically hold the microprocessor integrated circuit and provide electrical connections between the microprocessor and the remainder of the computer system via wirings etched in the PCB. These computer systems frequently rely on a single microprocessor to carry out all processing operations for the computer system. One drawback of the single microprocessor computer system is that the single processor effectively creates a bottleneck in the system thus limiting the overall speed and power of the computer.
As computer users require greater processing capabilities, the ability to upgrade to a faster microprocessor or to add additional functions or features becomes more important. One solution that computer developers have embarked upon to increase the performance of computer systems is to provide for the sharing of processing duties. It is now possible to add a math coprocessor chip to many computer systems which takes on many of the mathematical tasks for the central processing unit (CPU). Other enhancements that have been developed are graphics processors which handle the processing of graphical information to free the CPU to perform other tasks. These types of upgrades work in conjunction with and at the behest of the single CPU.
Other enhancements for computer systems include the use of two or more central processing units in what is known as a multiprocessing environment. When multiple processing units are implemented, they divide the processing work up to increase the overall performance of the computer system. Conventional multiprocessing systems are much more expensive than uniprocessing systems because the hardware to support multiple processors can be very complicated and the protocols for implementing multiprocessing are complex.
Another advance in making computer systems more powerful has been to design systems which can be readily upgraded simply by the addition of the various coprocessor chips described above. This will usually entail leaving on the PCB of the computer system one or several empty sockets which are coupled to the already present CPU (referred to as the computer system's original equipment manufacture (OEM) CPU). Each of the empty sockets is designed for a dedicated type of processor and the OEM CPU is equipped for dealing with each particular associated chip socket. For example, one socket might be dedicated for the optional addition of a math coprocessor while another socket might be for the use of a graphics coprocessor. Each of these processors may come from a different source than the computer system with the OEM CPU.
The present computer systems with dedicated expansion sockets leave many things to be desired. The nature and type of upgrade supported by a system must be preconceived at the time of system manufacturing. Many pins from the central processing unit are required for accommodating a plurality of different types of upgrade processors. The insertion of a math coprocessor chip into a socket dedicated for the use of a graphical coprocessor will not work. Likewise, a math coprocessor chip may not be added to the expansion socket for a graphics coprocessor. Further, to date no provision has been made for the creation of a multiprocessing system merely by the addition of a new processor without the addition of other supporting hardware.
One method of upgrading a computer system to use a more advanced CPU is described in co-pending U.S. patent application, "Method and Apparatus for Upgrading a Computer Processing System," Ser. No. 07/687,222 (now abandoned), filed Apr. 18, 1991 and assigned to the assignee of the present invention. That application discloses providing a dedicated upgrade socket solely for receiving an upgrade CPU. When the upgrade CPU is present, a signal is propagated from the upgrade socket to the original CPU indicating "upgrade present". The original CPU then shuts itself down and the upgrade CPU operates the computer system as a single processor system.
The reason the upgrade sockets have had to be dedicated to the various types of upgrade processors is that there has been no way for the CPU to determine what kind of processor has been inserted into an adjacent upgrade socket. It would be desirable, and is therefore an object of the present invention, to provide flexibility in the use of upgrade processors in upgrade sockets found on newly designed computer PCBs.